scholarly journals Opposing motors provide mechanical and functional robustness in the human spindle

2021 ◽  
Author(s):  
Lila Neahring ◽  
Nathan H. Cho ◽  
Sophie Dumont
Keyword(s):  
Cell Division ◽  
Design Principle ◽  
Microtubule Dynamics ◽  
Cellular Structures ◽  
Left Handed ◽  
Motor Activities ◽  
And Function ◽  
Bipolar Spindles ◽  
Shape And Size

SummaryAt each cell division, the spindle self-organizes from microtubules and motors. How the spindle’s diverse motors, often acting redundantly or in opposition, collectively give rise to its emergent architecture, mechanics, and function is unknown. In human spindles, the motors dynein and Eg5 generate contractile and extensile stress, respectively. Inhibiting dynein or its targeting factor NuMA leads to unfocused, turbulent spindles and inhibiting Eg5 leads to monopoles, yet bipolar spindles form when both are inhibited together. What, then, are the roles of these opposing motors? Here we generate NuMA/dynein- and Eg5-doubly inhibited spindles that not only attain a typical metaphase shape and size, but also undergo anaphase. However, these spindles have reduced microtubule dynamics and are mechanically fragile, fracturing under force. Further, they exhibit lagging chromosomes and dramatic left-handed twist at anaphase. Thus, while these opposing motor activities are not required for the spindle’s shape, they are essential to its mechanical and functional robustness. Together, this work suggests a design principle whereby opposing active stresses provide robustness to force-generating cellular structures.

scholarly journals The mitotic spindle protein CKAP2 potently increases formation and stability of microtubules

eLife ◽  
2022 ◽  
Vol 11 ◽  
Author(s):  
Thomas S McAlear ◽  
Susanne Bechstedt
Keyword(s):  
Cell Division ◽  
Growth Factor ◽  
Mitotic Spindle ◽  
Apparent Rate Constant ◽  
Microtubule Dynamics ◽  
Proliferation Marker ◽  
Microtubule Growth ◽  
Large Rearrangements ◽  
And Function

Cells increase microtubule dynamics to make large rearrangements to their microtubule cytoskeleton during cell division. Changes in microtubule dynamics are essential for the formation and function of the mitotic spindle, and misregulation can lead to aneuploidy and cancer. Using in vitro reconstitution assays we show that the mitotic spindle protein Cytoskeleton-Associated Protein 2 (CKAP2) has a strong effect on nucleation of microtubules by lowering the critical tubulin concentration 100-fold. CKAP2 increases the apparent rate constant ka of microtubule growth by 50-fold and increases microtubule growth rates. In addition, CKAP2 strongly suppresses catastrophes. Our results identify CKAP2 as the most potent microtubule growth factor to date. These finding help explain CKAP2's role as an important spindle protein, proliferation marker, and oncogene.

scholarly journals Thirty years of search and capture: The complex simplicity of mitotic spindle assembly

2015 ◽  
Vol 211 (6) ◽  
pp. 1103-1111 ◽  
Author(s):  
Rebecca Heald ◽  
Alexey Khodjakov
Keyword(s):  
Cell Division ◽  
Mitotic Spindle ◽  
Spindle Assembly ◽  
Microtubule Dynamics ◽  
Adaptive Changes ◽  
Bipolar Spindle ◽  
Chromosome Architecture ◽  
Self Assembling ◽  
Motor Activities ◽  
Mitotic Spindle Assembly

Cell division is enacted by a microtubule-based, self-assembling macromolecular machine known as the mitotic spindle. In 1986, Kirschner and Mitchison proposed that by undergoing dynamic cycles of growth and disassembly, microtubules search for chromosomes. Capture of microtubules by the kinetochores progressively connects chromosomes to the bipolar spindle. 30 years later, “search and capture” remains the cornerstone of spindle assembly. However, a variety of facilitating mechanisms such as regulation of microtubule dynamics by diffusible gradients, spatially selective motor activities, and adaptive changes in chromosome architecture have been discovered. We discuss how these mechanisms ensure that the spindle assembles rapidly and with a minimal number of errors.

scholarly journals The contribution of αβ-tubulin curvature to microtubule dynamics

2014 ◽  
Vol 207 (3) ◽  
pp. 323-334 ◽  
Author(s):  
Gary J. Brouhard ◽  
Luke M. Rice
Keyword(s):  
Cell Division ◽  
Mitotic Spindle ◽  
Fundamental Property ◽  
Microtubule Dynamics ◽  
Cellular Structures ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
Microtubule Growth ◽  
Microtubule Networks ◽  
And Control

Microtubules are dynamic polymers of αβ-tubulin that form diverse cellular structures, such as the mitotic spindle for cell division, the backbone of neurons, and axonemes. To control the architecture of microtubule networks, microtubule-associated proteins (MAPs) and motor proteins regulate microtubule growth, shrinkage, and the transitions between these states. Recent evidence shows that many MAPs exert their effects by selectively binding to distinct conformations of polymerized or unpolymerized αβ-tubulin. The ability of αβ-tubulin to adopt distinct conformations contributes to the intrinsic polymerization dynamics of microtubules. αβ-Tubulin conformation is a fundamental property that MAPs monitor and control to build proper microtubule networks.

scholarly journals Midbody: From the Regulator of Cytokinesis to Postmitotic Signaling Organelle

Medicina ◽  
2018 ◽  
Vol 54 (4) ◽  
pp. 53 ◽  
Author(s):  
Ieva Antanavičiūtė ◽  
Paulius Gibieža ◽  
Rytis Prekeris ◽  
Vytenis Skeberdis
Keyword(s):  
Stem Cells ◽  
Cell Division ◽  
Intercellular Bridge ◽  
Large Protein ◽  
Daughter Cells ◽  
First Case ◽  
Tumorigenic Potential ◽  
The One ◽  
And Function ◽  
Protein Rich

Faithful cell division is crucial for successful proliferation, differentiation, and development of cells, tissue homeostasis, and preservation of genomic integrity. Cytokinesis is a terminal stage of cell division, leaving two genetically identical daughter cells connected by an intercellular bridge (ICB) containing the midbody (MB), a large protein-rich organelle, in the middle. Cell division may result in asymmetric or symmetric abscission of the ICB. In the first case, the ICB is severed on the one side of the MB, and the MB is inherited by the opposite daughter cell. In the second case, the MB is cut from both sides, expelled into the extracellular space, and later it can be engulfed by surrounding cells. Cells with lower autophagic activity, such as stem cells and cancer stem cells, are inclined to accumulate MBs. Inherited MBs affect cell polarity, modulate intra- and intercellular communication, enhance pluripotency of stem cells, and increase tumorigenic potential of cancer cells. In this review, we briefly summarize the latest knowledge on MB formation, inheritance, degradation, and function, and in addition, present and discuss our recent findings on the electrical and chemical communication of cells connected through the MB-containing ICB.

scholarly journals Oligonucleotides DNA containing 8-trifluoromethyl-2′-deoxyguanosine for observing Z-DNA structure

2020 ◽  
Author(s):  
Hong-Liang Bao ◽  
Tatsuki Masuzawa ◽  
Takanori Oyoshi ◽  
Yan Xu
Keyword(s):  
Genetic Diseases ◽  
Dna Structure ◽  
2D Nmr ◽  
Living Cells ◽  
Molecular Probes ◽  
Alternative Form ◽  
Left Handed ◽  
Z Dna ◽  
And Function

Abstract Z-DNA is known to be a left-handed alternative form of DNA and has important biological roles as well as being related to cancer and other genetic diseases. It is therefore important to investigate Z-DNA structure and related biological events in living cells. However, the development of molecular probes for the observation of Z-DNA structures inside living cells has not yet been realized. Here, we have succeeded in developing site-specific trifluoromethyl oligonucleotide DNA by incorporation of 8-trifluoromethyl-2′-deoxyguanosine (FG). 2D NMR strongly suggested that FG adopted a syn conformation. Trifluoromethyl oligonucleotides dramatically stabilized Z-DNA, even under physiological salt concentrations. Furthermore, the trifluoromethyl DNA can be used to directly observe Z-form DNA structure and interaction of DNA with proteins in vitro, as well as in living human cells by19F NMR spectroscopy for the first time. These results provide valuable information to allow understanding of the structure and function of Z-DNA.

scholarly journals A Chromatin-associated Kinesin-related Protein Required for Normal Mitotic Chromosome Segregation in Drosophila

1997 ◽  
Vol 139 (6) ◽  
pp. 1361-1371 ◽  
Author(s):  
Isabel Molina ◽  
Sigrid Baars ◽  
Julie A. Brill ◽  
Karen G. Hales ◽  
Margaret T. Fuller ◽  
...  
Keyword(s):  
Cell Division ◽  
Gene Product ◽  
Chromosome Segregation ◽  
Mitotic Chromosome ◽  
Related Protein ◽  
Wild Type ◽  
Type Function ◽  
Microtubule Motor ◽  
Mitotic Figures ◽  
Bipolar Spindles

The tiovivo (tio) gene of Drosophila encodes a kinesin-related protein, KLP38B, that colocalizes with condensed chromatin during cell division. Wild-type function of the tio gene product KLP38B is required for normal chromosome segregation during mitosis. Mitotic cells in tio larval brains displayed circular mitotic figures, increased ploidy, and abnormal anaphase figures. KLP38B mRNA is maternally provided and expressed in cells about to undergo division. We propose that KLP38B, perhaps redundantly with other chromosome-associated microtubule motor proteins, contributes to interactions between chromosome arms and microtubules important for establishing bipolar attachment of chromosomes and assembly of stable bipolar spindles.

scholarly journals Eg5 is static in bipolar spindles relative to tubulin

2001 ◽  
Vol 154 (6) ◽  
pp. 1125-1134 ◽  
Author(s):  
Tarun M. Kapoor ◽  
Timothy J. Mitchison
Keyword(s):  
Motor Activity ◽  
Half Life ◽  
Microtubule Dynamics ◽  
Spindle Matrix ◽  
Spindle Poles ◽  
Kinesin Eg5 ◽  
Mitotic Kinesin Eg5 ◽  
Bipolar Spindles

We used fluorescent speckle microscopy to probe the dynamics of the mitotic kinesin Eg5 in Xenopus extract spindles, and compared them to microtubule dynamics. We found significant populations of Eg5 that were static over several seconds while microtubules flux towards spindle poles. Eg5 dynamics are frozen by adenylimidodiphosphate. Bulk turnover experiments showed that Eg5 can exchange between the spindle and the extract with a half life of <55 s. Eg5 distribution in spindles was not perturbed by inhibition of its motor activity with monastrol, but was perturbed by inhibition of dynactin with p50 dynamitin. We interpret these data as revealing the existence of a static spindle matrix that promotes Eg5 targeting to spindles, and transient immobilization of Eg5 within spindles. We discuss alternative interpretations of the Eg5 dynamics we observe, ideas for the biochemical nature of a spindle matrix, and implications for Eg5 function.

scholarly journals Numerical operations in living cells by programmable RNA devices

2019 ◽  
Vol 5 (8) ◽  
pp. eaax0835 ◽  
Author(s):  
Kei Endo ◽  
Karin Hayashi ◽  
Hirohide Saito
Keyword(s):  
Messenger Rna ◽  
Design Principle ◽  
Logic Gates ◽  
Living Cells ◽  
Multiple Biomarkers ◽  
Intracellular Changes ◽  
And Function ◽  
Single Living Cells ◽  
Single Living ◽  
Numerical Operations

Integrated bioengineering systems can make executable decisions according to the cell state. To sense the state, multiple biomarkers are detected and processed via logic gates with synthetic biological devices. However, numerical operations have not been achieved. Here, we show a design principle for messenger RNA (mRNA) devices that recapitulates intracellular information by multivariate calculations in single living cells. On the basis of this principle and the collected profiles of multiple microRNA activities, we demonstrate that rationally programmed mRNA sets classify living human cells and track their change during differentiation. Our mRNA devices automatically perform multivariate calculation and function as a decision-maker in response to dynamic intracellular changes in living cells.

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